Glaucoma is a disease in which the optic nerve is damaged, leading to progressive, irreversible loss of vision. It is typically associated with increased pressure of the fluid (i.e., aqueous humor) in the eye. Untreated glaucoma leads to permanent damage of the optic nerve and resultant visual field loss, which can progress to blindness. Once lost, this damaged visual field cannot be recovered. Glaucoma is the second leading cause of blindness in the world, affecting 1 in 200 people under the age of fifty, and 1 in 10 over the age of eighty for a total of approximately 70 million people worldwide.
The importance of lowering intraocular pressure (IOP) in delaying glaucomatous progression has been well documented. When drug therapy fails, or is not tolerated, surgical intervention is warranted. Surgical filtration methods for lowering intraocular pressure by creating a fluid flow-path between the anterior chamber and an area of lower pressure have been described. Intraocular shunts can be positioned in the eye to drain fluid from the anterior chamber to locations such as the sub-tenon's space, the subconjunctival space, the episcleral vein, the suprachoroidal space, Schlemm's canal, and the intra-scleral space.
Positioning of an intraocular shunt to drain fluid into the intra-scleral space is promising because it avoids contact with the conjunctiva and the supra-coroidal space. Avoiding contact with the conjunctiva and supra-choroid is important because it reduces irritation, inflammation and tissue reaction, that can lead to fibrosis and reduce the outflow potential of the subconjunctival and suprachoroidal space. The conjunctiva itself plays a critical role in glaucoma filtration surgery. A less irritated and healthy conjunctiva allows drainage channels to form and less opportunity for inflammation and scar tissue formation. Intra-scleral shunt placement safeguards the integrity of the conjunctiva and choroid, but may provide only limited outflow pathways that may affect the long term IOP lowering efficacy.